The magnetic field is extremely important for understanding the properties of the solar corona. However, there are still difficulties in the direct measurement of the coronal magnetic field. The magnetic-field-induced transition (MIT) in Fe x, appearing in coronal spectra, was discovered to have prospective applications in coronal magnetic field measurements. In this work, we obtained the extreme ultraviolet spectra of Fe x in the wavelength range of 174–267 Å in the Shanghai High-temperature Superconducting Electron Beam Ion Trap, and examined the effect of MIT in Fe x by measuring the line ratios between 257.262 Å and the reference line of 226.31 Å (257/226) at different magnetic field strengths for the first time. The electron density that may affect the 257/226 value was also obtained experimentally and verified by comparing the density-sensitive line ratio (175.266 Å/174.534 Å) measurements with the theoretical predictions, and there was good agreement between them. The energy separation between the two levels of 3s23p43d 4 D 5/2 and 3s23p43d 4 D 7/2, one of the most critical parameters for determining the MIT rate, was obtained by analyzing the simulated line ratios of 257/226 with the experimental values at the given electron densities and magnetic fields. Possible reasons that may have led to the difference between the obtained energy splitting and the recommended value in previous works are discussed. Magnetic field response curves for the 257/226 value were calculated and compared to the experimental results, which is necessary for future MIT diagnostics.
We present a new investigation of unidentified emission lines in 350–660 nm from W11+ at a compact electron-beam ion trap in Shanghai. To help the line identification, transition energies of the lowest 48 levels are calculated by the large-scale relativistic configuration interaction and multiconfiguration Dirac-Hartree-Fock calculation. The results from the two calculations are in good agreement with each other and the deviation is 0.66% on average. By using the collisional-radiative model implemented in the flexible atomic code, six observed lines for the visible spectrum of W11+ are identified as magnetic-dipole transitions from 4f125s25p3 and 4f135s25p2 configurations.
The precise measurement of the transition wavelength of the fine structure of highly charged ions can not only test basic physical theories including the quantum electrodynamics effect and the electronic correlation effect but also provide key atomic data for astrophysics and fusion plasma physics. Furthermore, highly charged ions are considered as a potential candidate for optical clocks with extremely ultra-high precision. In this work, a new spectral calibration system is built in a high-temperature superconducting beam ion trap (SH-HtscEBIT) in the Institute of Modern Physics, Fudan University, and the uncertainty of its spectrum wavelength measurement is evaluated by combining internal and external calibrations. The minimum wavelength uncertainty caused by the new spectral calibration system in the visible light band reaches 0.002 nm. On this basis, the precise measurement of 2s<sup>2</sup>2p <sup>2</sup>P<sub>1/2</sub>—<sup>2</sup>P<sub>3/2</sub> M1 transition wavelength for boron-like Ar<sup>13+</sup> is performed at the SH-HtscEBIT by utilizing the new calibration system. The experimentally measured transition wavelength is (441.2567 ± 0.0026) nm. It is currently the experimental result with the highest measurement accuracy of spectroscopy of highly charged ions at the SH-HtscEBIT, which lays the foundation for the precise measurement of the hyperfine splitting and isotope shift of highly charged ions in the future experiments.
We present a new investigation of unidentified emission lines in 350–660 nm from W11+ at a compact electron-beam ion trap in Shanghai. To help the line identification, transition energies of the lowest 48 levels are calculated by the large-scale relativistic configuration interaction and multiconfiguration Dirac-Hartree-Fock calculation. The results from the two calculations are in good agreement with each other and the deviation is 0.66% on average. By using the collisional-radiative model implemented in the flexible atomic code, six observed lines for the visible spectrum of W11+ are identified as magnetic-dipole transitions from 4f125s25p3 and 4f135s25p2 configurations.
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